EFFECT OF POTASSIUM ON VASODILATION TO ACETYLCHOLINE IN ESSENTIAL-HYPERTENSION

Patients with essential hypertension show impaired endothelium-depende nt vasodilation induced by acetylcholine. Because dietary potassium su pplementation increases endothelium-dependent relaxations to acetylcho line in hypertensive rats, we designed the present study to investigat e whether potassium increases endothelium-dependent vasodilation in es sential hypertensive patients. Therefore, in patients with essential h ypertension (n=13) and in normotensive control subjects (n=13) we eval uated the effect of intrabrachial potassium chloride (0.2 mmol/min) on forearm blood flow (strain-gauge plethysmography) modifications induc ed by intrabrachial acetylcholine (0.15, 0.45, 1.5, 4.5, and 15 mu g/1 00 mL forearm tissue per minute). In both groups of patients, potassiu m chloride infusion augmented local plasma potassium concentrations. F urthermore, in essential hypertensive patients but not in normotensive subjects it increased the vasodilating effect of the first three infu sion rates of acetylcholine. In contrast, in seven adjunctive essentia l hypertensive patients, potassium chloride did not alter intrabrachia l sodium nitroprusside-induced forearm vasodilation (1, 2, and 4 mu g/ 100 mL forearm tissue per minute). Finally, to evaluate the role of ni tric oxide on potassium-dependent facilitation of acetylcholine-induce d vasodilation in essential hypertension, we studied the effect of int rabrachial N-G-monomethyl L-arginine (100 mu g/ 100 mt per minute) in another group of seven hypertensive patients. Vasodilation to acetylch oline was again increased by potassium chloride; N-G-monomethyl L-argi nine slightly blunted the vasorelaxing effect of acetylcholine but abo lished the potentiating effect of potassium. These results indicate th at potassium increases endothelium-dependent vasodilation to acetylcho line in essential hypertensive patients but not in normotensive contro l subjects throughout the nitric oxide pathway and suggest that this e ffect might be a mechanism accounting for the beneficial effects propo sed for potassium in essential hypertension.